Love scenes in a book can be good (eg "Pride and Prejudice"). Sex scenes in a book are just tedious, to my mind. I might have found them stimulating when I was 14 years old. These days if I want porn, there are better ways to get it.

An old friend of mine once said this about the repetition (and gave me a bewildered look when I started laughing):

"Sex is the kind of thing you don't want to think about while you're doing it or it gets really strange. It's like plumbing or something."

Then again, anyone who can make it through a Robbe-Grillet novel probably won't mind. And sometimes the alienation created by scrutiny of sex becomes a statement on its own (J.G. Ballard's Crash).